Fixing element and ligament fixed with fixing element

ABSTRACT

Disclosed is a fixing element for connecting a ligament to a bone part of a human or animal. The fixing element includes a hollow, substantially cylindrical element fixable in a continuous opening in the bone part, and an engaging element for the ligament anchorable in the cylindrical element at least at two mutually differing axial positions.

The invention relates to a fixing element for connecting a ligament to abone part of a human or animal, comprising:

a hollow, substantially cylindrical element fixable in the continuousopening in the bone part, and

an engaging element for the ligament anchorable in the cylindricalelement at least at two mutually differing axial positions.

When a ligament is damaged, for instance a hamstring is torn (ligamentrupture) it is possible to arrange a new ligament surgically (plasticligament). For such a new ligament can be used ligament material removedfrom another location in the body, but plastic material (plasticligament) can also be employed for this purpose. The fixing of theligament can take place for instance by means of a screw with toothedring, staples, a bone plug, a toothed plug and so on. Fixing by means ofa bone plug entails a continuous opening being arranged in a bone partthrough which the ligament for fixing is placed, The bone segment comingfrom the bone part and used for making the continuous opening issubsequently placed in the ligament such that the ligament is clampedfixedly in the continuous opening by the bone segment or bone plug. Allthese fixing methods are frequently used singly or in combination.

Drawbacks of the existing fixing method are that it is difficult tobring the ligament to, and hold it at, the correct tension. Theconsequence hereof is reduced function, pain and a sensation ofinstability. A drawback which applies particularly to a ligamentmanufactured from a ligament material removed from another location inthe body (homologous) is that a ligament operatively arranged at thecorrect tension can slacken in the course of time whereby instabilityonce again increases. A drawback to plastic ligament material is thatthis has a finite life-span so that it generally breaks after a numberof years. The ligament will then have to be replaced and this is onlypossible by means of another major operation.

FR-A-2 663 837 describes a fixing element for connecting a ligament to abone part. The fixing element comprises a hollow cylindrical element,which is fixable in a continous opening in the bone part and an engagingelement for anchoring the ligament in the cylindrical element. Theengaging element comprises a screw for displacing the engaging elementin the cylindrical element.

The object of the present invention is to fix a ligament to a bone partsuch that it is very simple to hold the ligament to or vary tensionrespectively to replace a fixed ligament with another.

The present invention provides for this purpose a fixing element whichis characterized in that the inner wall of the cylindrical element isprovided with a profile for co-action with and axial positioning of theengaging element for the ligament.

See further page 2, line 14: “The outer wall ...” placed and this isonly possible by means of another major operation.

The object of the present invention is to fix a ligament to a bone partsuch that it is very simple to hold the ligament to or vary tensionrespectively to replace a fixed ligament with another.

The present invention provides for this purpose a fixing element forconnecting a ligament to a bone part of a human or animal, comprising:

a hollow, substantially cylindrical element fixable in the continuousopening in the bone part, and

an engaging element for the ligament anchorable in the cylindricalelement at least at two mutually differing axial positions. The outerwall of the cylindrical element is preferably provided with a profilefor a stable anchoring thereof in the bone part. The cylindrical elementforms the engaging option for the engaging element which is connected tothe ligament. The engaging element is connectable in relatively simplemanner to the cylindrical element whereby displacement of the engagingelement relative to the cylindrical element is comparatively simple torealize or whereby it in possible to release an engaging element withligament fixed thereto from the cylindrical element and to replace itwith a new ligament likewise provided with an engaging element,irrespective of the ligament type. It will be apparent that it is ofgreat importance herein that the cylindrical element be rigidlyconnected to the bone part. The operative technique to be used does notdiffer greatly from the usual technique. For a simple connection betweenthe cylindrical element and the engaging element the inner wall of thecylindrical element is preferably provided with a profile for co-actionwith the engaging element for the ligament. This internal profile canmore preferably be formed by internal screw thread. For a simple andgood coupling of the engaging element to the cylindrical element theouter side of the engaging element is preferably also provided with aprofile for co-action with the inner side of the cylindrical element.This profile is preferably also formed by a screw thread. Readjustmentof the ligament tension can take place for instance using a limitedsurgical operation such as for instance with an incision under localanaesthetic. In a preferred embodiment it is possible to provide thefixing element with adjusting means controllable from a distance. Hereincan be envisaged for instance micromotors or induction principles. Thetension on the ligament can then be adjusted “in the field” using aremote control or on a production line or while the patient is connectedup to a knee laxity measuring apparatus. Other solutions are alsoconceivable in this respect, such as for instance temperature-sensitivematerials or adjusting means controllable by means of a moving magneticfield.

Owing to the construction with the hollow cylindrical element which ispermanently anchorable in the bone, the actions required for a possiblerevision are very limited and the revision time can be markedly reducedcompared with the revision time for an existing ligament anchoring. Therevision can be performed arthroscopically.

On at least one side of the cylindrical element the inner sidepreferably transposes smoothly into the end wall of the cylindricalelement. When the cylindrical element is placed in the bone part suchthat the smooth transition of the inner side into the end wall forms theside along which the ligament is carried into the cylindrical element,excessive wear of the ligament resulting from contact with a sharp edgecan be prevented.

The engaging element is preferably provided with means for clamping theligament. Clamping of the ligament has the advantage that the ligamentmaterial is hereby not damaged, or hardly so, and that the ligamentlength required for a particular operation remains as limited aspossible. The engaging element can be used irrespective of the type ofimplant (homologous, plastic ligament or combination).

In a preferred embodiment the engaging element comprises a continuousopening in which a clamping element is anchorable for clamping theligament. Such a clamping construction is very reliable and moreoversimple in use.

In another preferred embodiment the engaging element is connectable tothe cylindrical element with interposing of a resilient element. Bymeans of such a resilient connection the ligament tension can be heldconstant despite for instance stretching of the ligament materialoccurring in the course of time. Another advantage is that peak loads onthe ligament can be at least partially absorbed by the resilientelement, whereby damage to a ligament will occur less quickly.

In yet another preferred embodiment the engaging element is provided onthe side remote from the ligament with at least one recess and/orprojecting part for engagement of adjusting means for altering theposition of the engaging element relative to the cylindrical element. Bymeans of this provision it becomes possible to vary the tension on theligament post-operatively using a very small incision. By inserting anadjusting means, for instance in the form of a spanner, into theincision such that it co-acts with the recess and/or projecting part itbecomes possible to alter the position of the engaging element relativeto the cylindrical element. A major surgical operation is therefore nolonger necessary to change the tension on the ligament.

The invention also relates to a ligament fixed with at least one fixingelement to a bone part. It is possible to anchor the ligament on twosides with the fixing elements according to the invention but asignificant advantage can already be achieved when one side of theligament is fixed with the fixing elements according to the inventionwhile the other side can be fixed according to a method of the priorart.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further elucidated with reference to thenon-limitative embodiments shown in the following figures. Herein:

FIG. 1 shows a cut away perspective view of a knee provided with aligament fixed on one side with a fixing element according to theinvention.

FIG. 2 is a perspective view of a fixing element according to theinvention, and

FIG. 3 is a perspective view of another fixing element according to theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shown a knee joint 1 of a human body which is partly cut away. Aligament 2 is fixed artificially in knee joint 1. Arranged for thispurpose in both an upper bone part 3 and a lower bone part 4 arerespective continuous openings 5, 6. Ligament 2 is fixed to lower bonepart 4 by means of a staple 7 known in the prior art. Such a connectionof ligament 2 to lower bone part 4 provides a rigid connection which canonly be released by way of a surgical operation. It is also difficultherein to fix the same staple 7 for a second time at the same positionon lower bone part 4.

In upper bone part 3 a fixing element 8 according to the invention isarranged in the continuous opening 5. The side of the fixing elementfacing toward ligament 2 is provided with an edge 9 rounded on theinside to prevent wear of ligament 2 where it enters fixing element 8.Reference is made to the following figures for a further elucidation offixing element 8.

FIG. 2 shows a fixing element 10 received in a bone part 3. Fixingelement 10 comprises a cylindrical element 11, the outer side of whichis provided with a profiled edge for a stable fixing of cylindricalelement 11 in the bode material 3. Cylindrical element 11 takes athollow form such that the inner wall is provided with an internal screwthread 12. Situated in cylindrical element 11 is an engaging element 13provided with an external screw thread 14, which screw thread 14 co-actswith internal screw thread 12 of cylindrical element 11. By rotatingengaging element 13 relative to cylindrical element 11 the former willbe displaced in axial direction. This axial displacement of engagingelement 13 will change the tension on the ligament 2. By placing forinstance a spanner 15 in recesses 16 arranged in the end wall ofengaging element 13 the tension on the ligament 2 can be varied in verysimple manner. Ligament 2 as shown in these figures is constructed froma large number of fibres 17. Other ligaments are however alsoconceivable. For fixing of engaging element 13 to ligament 2 theengaging element 13 is provided with a recess 18 in which a clampingelement 19 is situated. Clamping element 19 can be anchored in recesses18 such that the fibres 17 of ligament 2 are clamped between clampingelement 13 and the wall of the recess. In this figure the clampingelement is provided for this purpose with a screw thread which co-actswith an internal screw thread arranged over a part of the length ofrecess 18. Other solutions can however also be envisaged herefor.

FIG. 3 shows a fixing element 20 with a construction which differs fromthe fixing element 10 shown in FIG. 2. The fixing element 20 shown herelikewise comprises a cylindrical element 11 which corresponds with theelement shown in FIG. 2. On the side where ligament 2 can come intocontact with cylindrical element 11 the latter is provided with arounded edge 21. Situated in cylindrical element 11 is an engagingelement 22 with a hollow jacket 23, this latter being provided with anexternal screw thread 24 for co-action with internal screw thread 12 ofcylindrical element 11. By rotating fixing element 20, which issimplified by a protrusion 25 mounted on jacket 23, the position of thejacket 23 can be varied in an axial direction relative to cylindricalelement 11. At variance with the construction as shown in FIG. 2, aclamping block 26 greatly resembling clamping element 19 as shown inFIG. 2 is received for free axial movement in jacket 23. The operationof the clamping block will not be further elucidated in these figures.Clamping block 26 supports by means of a spring 27 on jacket 23. Thetension on ligament 2 will hereby remain constant in the case of smallchanges in the length of ligament 2; the changes in length of ligament 2can be absorbed by the spring 27. The fixing element 20 shown in thisfigure therefore has the advantage that in the case of small changes inthe length of the ligament 2 readjustment do not have to be carried outin order to retain a constant tension on ligament 2.

What is claimed is:
 1. A fixing element for connecting a ligament to ahuman or animal bone part, comprising: a hollow, substantiallycylindrical element fixable in a continuous opening through the bonepart and extending substantially a full length of the opening; and acylindrical engaging element for the ligament, the engaging elementpositioned axially within the cylindrical element wherein an inner wallof the cylindrical element is provided with a profile for co-action witha profiled outer wall of the engaging element such that the engagingelement is displaceable axially relative to the cylindrical element forchanging tension of the ligament.
 2. The fixing element as claimed inclaim 1, wherein the profile of the inner wall of the cylindricalelement is formed by an internal screw thread.
 3. The fixing element asclaimed in claim 1, wherein an outer wall of the cylindrical element isprovided with a profile for anchoring the cylindrical element in thebone part.
 4. The fixing element as claimed in claim 1, wherein thefixing element is provided with adjusting means for axially displacingthe engaging element relative to the cylindrical element and changingthe tension of the ligament.
 5. The fixing element as claimed in claim1, wherein at least one end face of the cylindrical element transposessmoothly into the inner wall of the cylindrical element.
 6. The fixingelement as claimed in claim 1, wherein the engaging element is providedwith means for clamping the ligament.
 7. The fixing element as claimedin claim 1, wherein the profiled outer wall of the engaging element isformed by a screw thread.
 8. The fixing element as claimed in claim 1,wherein the engaging element includes a continuous opening in which aclamping element is anchorable for clamping the ligament.
 9. The fixingelement as claimed in claim 1, wherein the engaging element isconnectable to the cylindrical element with the interposing of aresilient element.
 10. The fixing element as claimed in claim 1, whereinthe engaging element is provided on a side remote from the ligament withat least one recess for engagement of adjusting means for changing theaxial position of the engaging element relative to the cylindricalelement.
 11. The fixing element as claimed in claim 1, wherein theengaging element is provided on a side remote from the ligament with atleast one projecting part for engagement of adjusting means for changingthe axial position of the engaging element relative to the cylindricalelement.